1. Field of Invention
The present invention relates to a liquid crystal display apparatus. More particularly, the present invention relates to a liquid crystal display apparatus with a wide viewing angle.
2. Description of Related Art
Liquid crystal display (LCD) screens are popular among consumers because of their many advantages, such as low cost, high resolution and high stability. There are many digital display devices/technologies that have been developed recently. The Twisted Nematic (TN) LCD screen and the Multi-domain Vertical Alignment (MVA) LCD screen are examples of such digital display devices/technologies.
In an LCD module, a liquid crystal cell (LC cell) is disposed between two opposing transparent conductive films. The movement of the liquid crystals is controlled by an electric field and the electric field lines between these two opposing transparent conductive films. The liquid crystal cell may cooperate with upper and lower polarization films to adjust the transmittance of light generated by a backlight source.
The size of a pixel unit in a high definition LCD device is very small. For example, the size of one pixel unit is only 34.5 μm×103.5 μm in a 3.5-inch LCD device with an 80×480 resolution. In this case, only a part of the projecting light may penetrate the pixel unit. The ratio of light penetrating the pixel unit (aperture ratio) in a traditional LCD device is very low. In a traditional LCD device manufactured by a five-mask process, the aperture ratio is about 38%.
There are wave-shaped protruding portions disposed on a transparent conductive film in a Multi-domain Vertical Alignment (MVA) LCD device with a wide viewing angle. However, the protruding portions will damage the aperture ratio of the pixel units. In order to elevate the aperture ratio of the pixel units, the Patterned Vertical Alignment (PVA) process is adopted in the display device with a wide viewing angle, because the protruding portions in the MVA process may damage the aperture ratio and have a minimal size limitation (e.g., the width of the transparent conductive film with the protruding portion can not be smaller than 16 μm in general) due to limitations encountered during manufacture. In comparison, the Patterned Vertical Alignment (PVA) process utilizes a transparent conductive film with round or elongated Indium Tin Oxide (ITO) slits, and the width of the transparent conductive film can be 10 μm or less.
In a practical application, the difference between aperture ratios realized when using the MVA process employing protruding portions and the PVA process employing ITO slits can reach 10% in a 4-inch LCD device with an 800×480 resolution.
However, after the transparent conductive film of the color filter substrate in the PVA process is patterned (i.e., by forming slits or holes), the slits or holes will allow some external electric fields or electric field lines to enter the liquid crystal layer to thereby interfere with the liquid crystal behavior of the liquid crystal layer. In particular, the liquid crystal cells in In-Plane Switching (IPS) devices or Fringe Field Switching (FFS) devices will be affected by external electric fields or electric field lines because there is no transparent conductive film on their color filters. For example, after a finger contacts the surface of the LCD device, electrostatic charges from the finger will remain on the surface of the LCD device and continuously interfere with the displaying function of the LCD device. This will result in a whitened area or an uneven brightness on the panel.
In other words, display panels with ITO slits on the transparent conductive film of the color filter substrate may have advantages of higher aperture ratio and thinner size, but also have disadvantage of the displaying function being affected by external electric fields or electrostatic charges accumulated on the surface.
In order to solve the aforesaid problems, a prior art solution involves the use of a transparent conductive film which is connected to a fixed voltage and disposed on the outer surface of a color filter substrate. With the use of this solution, electrostatic charges accumulated on the surface are dispersed and external electric fields are shielded. However, such a solution involves a process on the back side of the color filter substrate. Since traditional equipment usually focuses on a process performed on the inner surface of the color filter substrate, the process performed on the back side thereof requires the use of extra equipment, and therefore additional investment is required. Furthermore, the transparent conductive film (ITO conductive film) exposed on the outer surface of the color filter substrate may be scratched or damaged during manufacture or user operation, such that the yield rate and the lifetime of the product are reduced.